By Randall Osborne

Two major collaborations on drugs for cancer — both begun last year, and worth a total of $125 million — are dissolving, one by mutual agreement and the other by the exercise of an option that was part of the deal.

Agouron Pharmaceuticals Inc., of La Jolla, Calif., has agreed to end its pact with Basel, Switzerland-based F. Hoffman-La Roche Ltd., after an informal interim analysis of Phase II/III trials of Thymitaq (nolatrexed dihydrochloride, also known as AG337), which Agouron said it will quit developing.

Since June 1996, the companies have been partnered to develop Thymitaq and AG3340, another cancer drug. The deal was potentially worth well over $75 million in license fees, milestone payments and sales profits. (See BioWorld Today, June 21, 1996, p. 1.)

Agouron said that, although Thymitaq, which inhibits the enzyme thymidylate synthase, seems to work as a single agent in head, neck and liver cancers, it's not sufficiently better than existing therapies to justify continuing its development.

The company said it will move ahead with AG3340, which is one of a class of drugs that inhibit selected matrix metalloprotease enzymes, and with AG2034, a small-molecule compound designed to inactivate an enzyme called glycineamide ribonucleotide transformylase. Both are expected to begin more definitive efficacy trials early next year.

Roche still will market Agouron's HIV protease inhibitor, Viracept (nelfinavir mesylate) in some international territories, as arranged in a separate deal.

Agouron's stock (NASDAQ:AGPH) closed Tuesday at $31, down $8.50, or 21.5 percent.

Another partnership is ending between Megabios Corp., of Burlingame, Calif., and New York-based Pfizer Inc. Their four-year deal, worth $50 million in equity investments, focused on intravenous treatment of solid tumors by way of inhibiting angiogenesis (new blood vessel formation), thus stopping their blood supply. (See BioWorld Today, June 18, 1996, p. 1.)

Megabios said the program has good market potential and a sound scientific basis. The company, which in September raised $30 million in its initial public offering, said it will keep developing gene-based cancer therapies, with no disruption in the program expected.

Pfizer is required to give six months' notice when terminating the deal and will continue its funding through May 1998.

Megabios' stock (NASDAQ:MBIO) closed Tuesday at $11.375 down $2.625, an 18.7 percent drop. Pfizer's shares (NASDAQ:PFE) closed at $76.312, up $0.312. *